1. Technical Field
The present disclosure relates to nanomaterials, and specifically to copper indium selenide (CIS) nanorods and nanowires, and methods for making and using such nanorods and nanowires.
2. Technical Background
Copper indium selenide (CuInSe2; CIS) and related materials can be useful as light absorbing materials in, for example, photovoltaic (PV) devices. In photovoltaic devices, these materials can be useful due to their match to the solar spectrum and high optical absorption coefficients. The efficiency of most single junction thin-film solar cells is limited, and even those employing a CIS absorber layer can have a solar energy conversion of about 20% or less. CIS can exhibit good long-term stability that can improve with time. CIS films for photovoltaics are currently deposited onto substrates by a coevaporation process, in which copper, indium, and gallium metal are first deposited, then reacted with Se vapor or H2Se to convert the deposited materials to CIS. This deposition approach can be expensive and the CIS stoichiometry can be difficult to control when trying to deposit the films over large areas.
Solution-based methods have been developed to synthesize colloidal nanocrystals of many different materials, including metals, and Group II-VI, III-V, I-VI, and IV semiconductors. Colloidal CdSe and CdTe nanocrystals have been used to form functional photovoltaic devices with reasonable light energy conversion efficiencies; however, many Group II-VI semiconductors that would be useful for photovoltaic devices, such as CdTe for example, contain toxic Pb, Cd, and Hg, which make them undesirable for widespread commercialization.
Synthetic procedures for preparing colloidal CuInSe2 and CIGS nanocrystals have been reported in the literature, but these procedures typically have low yield and produce particles having multiple phases. The performance of traditional nanocrystal solar cells can also be inhibited by the high number of interfaces present in the material. Thus, there is a need to address the aforementioned problems and other shortcomings associated with traditional CIS synthesis and their incorporation into devices. These needs and other needs are satisfied by the compositions and methods of the present disclosure.